The Core will support several basic functions of this program, including: (1) maintenance of a well-characterized group of HIV-1 seropositive subjects; (2) maintenance of a data acquisition, management, and analysis unit to manage a centralized database system and provide support for statistical analysis; (3) maintenance of a repository for clinical cerebrospinal fluid (CSF) and blood specimens characterized by "routine" virological and immunological assessments; and (4) maintenance of a pathological specimen processing unit and library, including characterization of tissue by "routine" pathological and immunohistochemical methods.